Scanning unit and scanning microscope having the same

ABSTRACT

A scanning unit for moving an object to be moved along at least one axis, which comprises a first actuator for moving the object along a first axis, the first actuator having a pair of end portions, and the object being attached to one of the end portions, the first actuator being held at a position in the vicinity of the center in dimension or the center of gravity thereof.

This is a Division of application Ser. No. 09/803,448, filed Mar. 9,2001 now U.S. Pat. No. 6,617,761.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2000-71128, filed Mar. 14,2000; and No. 2001-34391, filed Feb. 9, 2001, the entire contents ofboth of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a scanning microscope or a scanningunit to which a technique of a scanning microscope is applied and whichis used in an apparatus for observing or processing a sample or forrecording information. More particularly, the present invention relatesto a scanning microscope using this scanning unit.

A stage mechanism for causing translational movement or rotationalmovement of an object is one of the basic elements of a machinemechanism. Further, an automatic stage capable of controlling stagemovement by using a drive mechanism such as a motor in accordance with acontrol signal such as an electrical signal is used in every scene.

A machine mechanism for repeatedly causing reciprocating translationalmovement or forward or backward rotational movement of an object in arelatively short period of time is also referred to as a scanning unit.Here, such a machine mechanism will be simply referred to as a scanningunit unless otherwise specified.

Such a scanning unit is mounted in, for example, a scanning microscope.As a scanning microscope apparatus in which such a scanning unit ismounted, there are a scanning probe microscope, a later scanningmicroscope, or an electronic scanning microscope which is of a typecapable of obtaining an image by scanning a sample with an electronicbeam being fixed.

A scanning probe microscope (SPM) is a scanning microscope whichmechanically scans a mechanical probe to obtain information of a samplesurface, and includes a scanning tunneling microscope (STM), an atomforce microscope (AFM), a scanning magnetic force microscope (MFM), ascanning electric capacity microscope (ScaM), a scanning near-fieldoptical microscope (SNOM), a scanning thermal microscope (SThM) andothers. In recent years, a nano-indentator and the like, which makes anindentation by pressing a probe made of diamond against a sample surfaceand checks hardness and the like of the sample by analyzing how theindentation is made, is regarded as one of the SPMs widely used,together with the above-described various microscopes.

The scanning probe microscope can obtain surface information in adesired sample area through a mechanical probe while performing relativeraster scanning or XY scanning with respect to the mechanical probe andthe sample, thereby mapping the obtained information on a TV monitor.Further, an SNOM and the like can perform fine processing or opticalinformation recording by causing a light beam emitted from an end of amechanical probe to act on a workpiece. Furthermore, a nano-indentatorcan form irregularities on a sample surface to similarly perform fineprocessing or information recording.

In such a scanning probe microscope, a relative position along the Zaxis of the sample and the probe, i.e., a distance between the sampleand the probe is subjected to feedback control in such a manner that theinteraction of the sample and the probe becomes constant during XYscanning. The movement along the Z axis is different from regularmovement along the X axis and the Y axis but irregular in order toreflect the surface shape or surface state of the sample. The movementalong the Z axis is generally referred to as Z scanning. The Z scanninghas a highest frequency among those of XYZ scanning. A frequency of Xscanning by the scanning probe microscope ranges from approximately 0.05to 200 Hz, and a frequency of Y scanning corresponds to (the frequencyof X scanning)/(Y scanning lines). A number of Y scanning lines is 10 to1000. Furthermore, a frequency of Z scanning is approximatelyseveral-fold to 100-fold of pixels per one line of X scanning withrespect to a frequency of X scanning.

For example, in order to fetch an image having 100 pixels along the Xaxis and 100 pixels along the Y axis in one second, a frequency of Xscanning is 100 Hz; a frequency of Y scanning, 1 Hz; and a frequency ofZ scanning is not less than 10 kHz. It is to be noted that a scanningfrequency of this example is presently the highest scanning frequencyfor the scanning probe microscope, and the frequency of X scanning isusually approximately several Hz. The scanning unit must be stableagainst external vibrations, and vibrations generated from the scanningunit itself by the internal scanning operation must be suppressed inorder to realize such a high scanning frequency as in this example.

The scanning unit is driven by vibrating a support portion supportingthe scanning unit as a counteraction. The vibration of the supportportion again acts on the scanning unit to vibrate an object. Therefore,the scanning unit requiring accurate positional control for the objectmust suppress the generation of such vibrations as much as possible.Although one effective method for suppressing the occurrence ofvibrations is to slowly move the object, this goes against the necessityfor repeatedly moving the object in a short period of time required inthe scanning unit.

BRIEF SUMMARY OF THE INVENTION

A main object of the present invention is to provide a scanning unitcapable of suppressing generation of vibrations and thereby effectingaccurate positional control.

Another object of the present invention is to provide a scanningmicroscope using such a scanning unit.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 shows a scanning probe microscope having a scanning unitaccording to a first embodiment;

FIG. 2A is a perspective view of a scanning unit illustrated in FIG. 1,which shows the scanning unit upside down for easy understanding, FIG.2B is a side view of the scanning unit shown from a Z direction, FIG. 2Cis a side view of the scanning unit shown from a Y direction, and FIG.2D is a side view of the scanning unit shown from an X direction;

FIG. 3A is a drawing for explaining the operation of the scanning unitillustrated in FIGS. 2A to 2D, and FIG. 3B is a drawing for explainingthe operation of a scanning unit of a second embodiment according to thepresent invention;

FIG. 4A is a perspective view of a scanning unit of a third embodimentaccording to the present invention, which shows the scanning unit upsidedown for easy understanding, and FIG. 4B is a side view of the scanningunit shown from the X direction;

FIG. 5A is a perspective view of a scanning unit of a fourth embodimentaccording to the present invention, which shows the scanning unit upsidedown for easy understanding, and FIG. 5B is a partial cross-sectionalside elevation of the scanning unit;

FIG. 6A is a plane view of a scanning unit of a fifth embodimentaccording to the present invention, and FIG. 6B is a cross-sectionalview of the scanning unit taken along the line Lx;

FIG. 7A is a perspective view of a scanning unit of a comparativeexample 1 according to a prior art for facilitating understanding thescanning unit according to the present invention, and FIG. 7B is apartial cross-sectional side elevation of the scanning unit;

FIG. 8A is a perspective view of a scanning unit of a comparativeexample 2 according to the prior art for facilitating understanding thescanning unit according to the present invention, and FIG. 8B is apartial cross-sectional side elevation of the scanning unit;

FIG. 9A is a perspective view of a scanning unit of a comparativeexample 3 according to the prior art for facilitating understanding thescanning unit according to the present invention, and FIG. 9B is apartial cross-sectional side elevation of the scanning unit;

FIG. 10A is a perspective view of a scanning unit of a sixth embodimentaccording to the present invention, FIG. 10B is a view of the scanningunit shown from the direction of arrow A, and FIG. 10C is a view of thescanning unit shown from the direction of arrow B;

FIG. 11 is a view for explaining the operation of a scanning unit of aseventh embodiment according to the present invention; and

FIG. 12A is a perspective view of a scanning unit of an eighthembodiment according to the present invention, and FIG. 12B is a view ofthe scanning unit shown from the direction of arrow C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 1 shows a mechanical scanning microscope, i.e., a scanning probemicroscope having a scanning unit of a first embodiment according to thepresent invention.

In FIG. 1, a scanning probe microscope 100 basically has a partcorresponding to a scanning probe microscope function and a partcorresponding to an optical microscope function.

The part corresponding to the scanning probe microscope functionincludes: a case 101; an optical sensor unit 102; a sensor unit Z stage103; a slide glass 104; a slide glass holding portion 105; a cantileverchip 106; a scanning unit holding base 107; a scanning unit 200; anactuator drive circuit 112; a scanning control circuit 113; a feedbackcircuit 114; an AC/DC conversion circuit 115; an oscillation circuit116; a pre-amp circuit 117; a semiconductor laser drive circuit 118; acomputer 119; and a TV monitor 120.

Further, the part corresponding to the optical microscope functionincludes: an optical illuminating system for microscope observation 110including a light source lamp 139 and a lens 138; an optical observationsystem for microscope observation 111 including an eyepiece 140; a halfprism 137; a microscope illuminating lamp power supply 121; and anobjective 122 of the optical sensor unit 102 shared with the partcorresponding to the scanning probe microscope function.

Further description will be given as to the part of the scanning probemicroscope function. The scanning unit holding base 107 is supported atthree points on the case 101 by three micrometer heads 135 (only twomicrometer heads are shown in FIG. 1) which can be manually fed by asmall amount. Furthermore, the scanning unit 200 is supported on thescanning unit holding base 107, and a sample 109 is attached to thescanning unit 200 in such a manner that the sample 109 faces downwards,namely, it is opposed to the cantilever chip 106 side. The scanning unit200 applies micromotion scanning to the sample 109 along the X axis, theY axis and the Z axis. The details of the scanning unit 200 will befully explained later. The scanning unit 200 may include an adjustmentmechanism for effecting rough adjustment of positions of a probe 132 ofthe cantilever chip 106 and the sample 109 in regard to each of the Xaxis, the Y axis and the Z axis.

The optical sensor unit 102 measures movement of a cantilever 131 of thecantilever chip 106. This is an optical sensor which is of an opticallever type. The optical sensor unit 102 has: an objective 122; anobjective supporting base 123; a prism 124; a polarized beam splitter125; a collimator lens 126; a semiconductor laser 127; a laser positionadjustment stage 128; a two-split photodiode 129; a photodiode positionadjustment stage 130.

A light ray emitted from the semiconductor laser 127 is turned into aparallel beam by the collimator lens 126 and then reflected by thepolarized beam splitter 125. Thereafter, this light beam is furtherreflected by the prism 124 and enters the objective 122. The parallelbeam is condensed on a rear surface of the cantilever 131 of thecantilever chip 106 by the objective 122. The light beam reflected bythe rear surface of the cantilever proceeds in the opposite direction.It passes through the polarized beam splitter 125 and further goesstraight to reach the two-split photodiode 129. The angle displacementof the cantilever 131 is reflected on movement of a light spot on thetwo-split photodiode 129 and outputted as an electric signal.

The objective 122 of the optical sensor unit 102 constitutes the opticalilluminating system for microscope observation 110 and the opticalobservation system for microscope observation 111 as well as the opticalsystem for optical microscope observation. The objective 122 is anobjective for use in an optical microscope and has, for example, atwenty-fold magnification.

The sensor unit Z stage 103 is provided for performing rough adjustmentof a position of the optical sensor unit 102 including the objective122. The sensor unit Z stage 103 moves the objective 122 included in theoptical sensor unit 102 up and down to effect focusing of the opticalsensor or focusing for microscope observation.

The slide glass holding portion 105 holds the slide glass 104. Apiezoelectric excitation device 133 for exciting the cantilever 131 isfixed to the slide glass holding portion 105 at a position apart from anattachment portion for the cantilever chip 106. An alternating voltagein the proximity of a resonance frequency of the cantilever 131 isapplied to the piezoelectric excitation device 133. The piezoelectricexcitation device 133 vibrates in accordance with the application ofthis voltage, and this vibration is transmitted to the cantilever chip106 to vibrate the cantilever 131.

In measurement for vibrating the cantilever 131 in this manner, adisplacement signal of the cantilever outputted from the optical sensorunit 102 becomes alternated. The AC/DC conversion circuit 115 convertsthis signal into a direct-current signal. In measurement in which thecantilever 131 is not vibrated, this circuit may be bypassed so that itdoes not operate.

Moreover, FIG. 1 shows the state of observation in a liquid. Water 134drips from the vicinity of the sample 109 of the scanning unit 200 tothe proximity of the slide glass 104 to which the cantilever chip 106 isfixed. Both the sample 109 and the cantilever chip 106 are positioned inwater. In the case of performing measurement in air, the water 134 isnot necessary.

As shown in FIG. 1, the scanning probe microscope 100 includes anelectric circuit and the like for controlling/driving the apparatus. Theoperation of these circuits is similar to the circuit operation in thescanning probe microscope which has been conventionally proposed.

A control signal of XYZ scanning is supplied from the computer 119 tothe scanning control circuit 113. Reference character “Z” in FIG. 1denotes a signal for adjusting a distance between a Z scanning actuatorof the scanning unit 200 and the probe 132 of the cantilever chip 106.The signal “Z” is mainly outputted from the computer when settingmeasurement conditions, for example, at the time of force curvemeasurement before carrying out measurement. In addition, the computer119 controls the oscillation circuit 116 to operate the piezoelectricexcitation device 133 and vibrates the cantilever 131 in the vicinity ofthe resonance frequency thereof.

When measurement starts, the actuator of the scanning unit 200 isscanned along the X axis and the Y axis based on a raster scanningcontrol signal (designated by “X” and “Y” in the drawing) outputted fromthe computer 119. The displacement of the cantilever 131 based on theinteraction of the probe 132 provided at the end of the cantilever 131and the surface of the sample 109 is detected by the optical sensor unit102, and the optical sensor unit 102 outputs the displacement signal.The displacement signal outputted from the optical sensor unit 102 isamplified by the pre-amp circuit 117 and inputted to the AC/DCconversion circuit 115. The AC/DC conversion circuit 115 extracts asignal having a frequency component of a reference signal from theoscillation circuit 116 and converts the alternating signal into adirect-current signal.

The feedback circuit 114 compares a setting signal directed by thecomputer 119 with an input signal from the AC/DC conversion circuit 115and transmits a Z feedback signal Zfb to the scanning control circuit113. The Z feedback signal Zfb serves as a scanning control signal ofthe Z direction actuator. The scanning control circuit 113 controls theactuator drive circuit 112 based on the Z feedback signal Zfb and drivesthe Z scanning actuator of the scanning unit 200. The computer 119processes surface information of the sample as three-dimensionalinformation based on scanning control signals “X” and “Y” generated bythe computer 119 itself and a signal from the feedback circuit 114 anddisplays the result on the TV monitor 120.

The scanning unit 200 of this embodiment will be further described indetail with reference to FIGS. 2A to 2D. As shown in FIGS. 2A to 2D, thescanning unit 200 comprises: a scanning unit holding base 201; actuatorpedestals 202 and 203 fixed to the scanning unit holding base 201; andactuators 204, 205 and 206 attached to the actuator pedestals 202 and203.

The actuator 204 is extendable along, for example, the X axis and issubstantially supported by the actuator pedestal 202 through theactuator holding portion 207. Similarly, the actuator 205 is extendablealong, for example, the Y axis and substantially supported by theactuator pedestal 203 through the actuator holding portion 208. Theactuator 206 is extendable along the Z axis and substantially supportedby the actuator pedestals 202 and 203 through the actuator holdingportion 209.

Each of the actuators 204, 205 and 206 comprises, for example, a stackedpiezoelectric device, and the piezoelectric device has, for example, alength of 10 mm and a cross section of 5 mm×3 mm. It extends andcontracts by 3 μm upon application of a voltage of 100 V. The actuators204, 205 and 206 extend and contract along the X axis, the Y axis andthe Z axis in accordance with application of a drive voltage through twolines extending therefrom, respectively.

The actuator holding portion 207 holds the actuator 204 at a position inthe vicinity of the center in dimension or the center of gravitythereof. The actuator holding portion 208 holds the actuator 205 at aposition in the vicinity of the center in dimension or the center ofgravity thereof. The actuator holding portions 209 and 210 hold theactuator 206 at a position in the vicinity of the center in dimension orof the center of gravity thereof.

To the actuator 206 is attached a sample holding portion 211 for holdingan object to be moved, for example, a sample. The sample holding portion211 has a sample base glass attached on an end surface thereof.

The actuator 204 extendable along the X axis has a minute ball 212attached on an end surface thereof facing the actuator 206 extendablealong the Z axis, and the minute ball 212 abuts and is attached on oneend portion side surface of the actuator 206 crossing the X axis.Similarly, the actuator 205 extendable along the Y axis has a minuteball 213 attached on an end surface thereof facing the actuator 206, andthe minute ball 213 abuts and is attached on one end portion sidesurface of the actuator 206 crossing the Y axis.

As described above, according to the scanning unit having the endsurfaces of the actuators being in contact with the object through theminute balls, the minute ball provided to the actuator which does notextend and contract serves as a guide with respect to the object anddoes not obstruct movement of the object by another actuator whichextends and contracts. Therefore, this scanning unit has an advantagethat the linearity of the operation characteristic is high.

The operation of the scanning unit 200 shown in FIGS. 2A to 2D along theZ axis will now be described with reference to FIG. 3A typicallyillustrating the scanning unit 200. FIG. 3A shows only members necessaryfor the following explanation.

In FIG. 3A, the actuator 206 comprises a stacked piezoelectric device,and its part close to the center in dimension or the center of gravityis fixed to the actuator pedestal 203 provided to the scanning unitholding base 201 by an actuator holding portion 210 made of siliconerubber having an adhesive effect. The both side portions of the stackedpiezoelectric device 206 extend and contract in opposed directions asshown by the arrows in accordance with application of a voltage with aposition in the vicinity of the center in dimension or the center ofgravity fixed to the actuator holding portion 210 as a reference.

In general, the operation of the actuator gives the vibrations or impactdue to the counteraction of the actuator operation to the actuatorholding portion holding this actuator. Such vibrations or impact resultsin oscillation of the scanning unit. In the case of scanning at highspeed or scanning using a high frequency, it is desirable to suppressthe vibrations of the scanning unit as much as possible.

In this embodiment, since a position of the actuator 206 in the vicinityof the center in dimension or the center of gravity thereof issupported, the impact is balanced on the boundary face between theactuator 206 and the actuator holding portion 210 indicated by a symbolX in the drawing, and the vibration transmitted to the actuator pedestal203 or the scanning unit holding base 201 can be suppressed. This can bebetter understood by comparing with the later-described comparativeexamples shown in FIGS. 7A, 7B, 8A, 8B, 9A and 9B.

Although the above has described suppression of generation of thevibrations concerning the Z scanning actuator 206, the occurrence of thevibrations can be similarly suppressed with respect to the X scanningactuator 204 and the-Y scanning actuator 205.

In the prior art scanning unit, the actuator such as a stackedpiezoelectric device described above usually has one end portion beingheld in order to assure a large scanning range, i.e., a long stroke.Thus, the counteraction of the operation of the actuator affects theholding portion, and this oscillates the scanning unit.

On the contrary, in the scanning unit in which the actuator is held at aposition close to the center in dimension or the center of gravity as inthis embodiment, since the part of the kinetic system close to thecenter of gravity is held, oscillation at the holding position can besuppressed. As a result, this scanning unit has less vibrations andstably operates with respect to scanning at high speed.

With the scanning probe microscope illustrated in FIG. 1, a sample (alatex ball having a diameter of 150 nm) in a liquid was able to bemeasured at an image fetching speed that an observation range on thesample surface 0.5 μm×0.5 μm is fetched at 0.5 second/screen, in datafetch of 100 pixels/line concerning the X axis and 100 lines (10,000pixels/screen) concerning the Y axis. A value of the image fetchingspeed 0.5 second/screen is a quite short period of time in the scanningprobe microscope. It is to be noted that a cantilever made of siliconnitride having a resonance frequency in a liquid of 395 kHz, a length of9 μm, a width of 2 μm and a thickness of 0.09 μm was used.

Additionally, since a commercially available actuator can be used as theactuator 206 without any modifications, the scanning unit of thisembodiment is advantageous in that the total cost can be reduced.

Second Embodiment

A second embodiment according to the present invention will now bedescribed with reference to FIG. 3B. FIG. 3B is a view corresponding toFIG. 3A and shows only members necessary for the following explanation.Further, in these drawings, like reference numerals denote like orcorresponding parts.

In the scanning unit of this embodiment, the Z scanning actuator 305 hasan actuator connection portion 308 consisting of, e.g., an aluminiumblock, and two stacked piezoelectric devices 306 and 307 connected tothis actuator connection portion 308. In general, the two stackedpiezoelectric devices 306 and 307 are widely commercially available, andthey are fixed to the actuator connection portion 308 by an adhesive sothat they can linearly extend with the actuator connection portion 308therebetween. Furthermore, a sample holding portion 211 is attached to afree end of the stacked piezoelectric device 306.

As can be understood from the similarity with FIG. 3A, since thescanning unit of this embodiment also has the actuator 305 being held ata position in the vicinity of the center in dimension or of the centerof gravity thereof, the scanning unit can stably operate with respect tohigh speed scanning with less vibrations.

Moreover, in the scanning unit of this embodiment, the actuatorconnection portion 308 sandwiched between the two stacked piezoelectricdevices 306 and 307 is held by the actuator holding portion 210 composedof, for example, silicone rubber. Therefore, the scanning unit of thisembodiment has an advantage that a difference in performance of thescanning unit hardly noticeable with respect to a quantity of siliconerubber used for attaching the actuator 305.

Third Embodiment

A third embodiment according to the present invention will now bedescribed with reference to FIGS. 4A and 4B. As shown in FIGS. 4A and4B, the scanning unit of this embodiment comprises: a scanning unitholding base 401; an L-shaped actuator pedestal 402 fixed to thescanning unit holding base 402; two actuators 403 and 404 attached tothe actuator pedestal 402; and an actuator 405 supported by the twoactuators 403 and 404.

Each of the actuators 403, 404 and 405 comprises, for example, a stackedpiezoelectric device and extendable along the X axis, the Y axis and theZ axis, respectively. Each of the X scanning actuator 403 and the Yscanning actuator 404 has one end portion being fixed to the actuatorpedestal 402. The highest scanning speed is demanded from the Z scanningactuator 405, and its part close to the center in dimension or thecenter of gravity is fixed and held to the other end portion of each ofthe X scanning actuator 403 and the Y scanning actuator 404 by anadhesive.

The Z scanning actuator from which the highest scanning speed isdemanded, i.e., the stacked piezoelectric device 405 has both sideportions symmetrically extending and contracting in the opposeddirections, as indicated by the arrows, with its part close to thecenter fixed to the X scanning actuator 403 and the Y scanning actuator404 as a reference. The impact generated due to the extending andcontracting operation of the stacked piezoelectric device 405 can be,therefore, suppressed. Accordingly, the scanning unit of this embodimentcan stably operate with respect to high speed scanning with lessvibrations.

In addition, the scanning unit of this embodiment has the followingadvantages as compared with the scanning unit of the first embodiment.In the scanning unit of the first embodiment, the X scanning and Yscanning actuators are pressed against the Z scanning actuator throughthe minute balls. Therefore, pressurization becomes insufficient duringextended use, and scanning along the X axis and the Y axis becomesunstable. On the contrary, in the scanning unit of this embodiment,since the Z scanning actuator 405 is fixed to the X scanning and Yscanning actuators 403 and 404 by the adhesive, scanning along the Xaxis and the Y axis hardly becomes unstable.

Fourth Embodiment

A fourth embodiment according to the present invention will now bedescribed with reference to FIGS. 5A and 5B. The scanning unit of thisembodiment comprises, as shown in FIGS. 5A and 5B, a scanning unitholding base 501, a cylindrical actuator 502 fixed to the scanning unitholding base 501, and another cylindrical actuator 503 supported by afree end of the actuator 502.

The cylindrical actuator 502 comprises, for example, a cylindricalpiezoelectric device, and such a cylindrical piezoelectric device isoften used in a commercially available scanning probe microscope. Thecylindrical piezoelectric device 502 has four split electrodes 504provided on an outer peripheral surface of a cylindrical piezoelectricmaterial and an opposed electrode provided on an inner peripheralsurface. The free end of the cylindrical piezoelectric device 502 can bescanned along the X axis and the Y axis by appropriately applying avoltage between these electrodes.

The cylindrical actuator 503 comprises also, for example, a cylindricalpiezoelectric device, and this is smaller than the cylindricalpiezoelectric device 502 and has a higher resonance frequency than thatof the cylindrical piezoelectric device 502. The cylindricalpiezoelectric device 503 has one electrode provided on an outerperipheral surface of a cylindrical piezoelectric material and oneelectrode provided on an inner peripheral surface. The free end of thecylindrical piezoelectric device 503 can be scanned along the Z axis byappropriately applying a voltage between both electrodes.

The cylindrical piezoelectric device 503 is held at a position in thevicinity of the center in dimension or of the center of gravity thereofby a member provided at the free end of the cylindrical piezoelectricdevice 502. Therefore, both side portions of the cylindricalpiezoelectric device 503 symmetrically extend and contract in opposeddirections, in accordance with application of a voltage between theelectrodes, as indicated by the arrow, with its part close to the centerfixed to the cylindrical piezoelectric device 502 as a reference. It is,therefore, possible to suppress the impact generated due to theextending and contracting operation of the cylindrical piezoelectricdevice 503 responsible for high speed scanning along the Z axis. Thescanning unit of this embodiment can, thus, stably operate with respectto high speed scanning with less vibrations.

Fifth Embodiment

A fifth embodiment according to the present invention will now bedescribed with reference to FIGS. 6A and 6B. As shown in FIGS. 6A and6B, the scanning unit of this embodiment comprises an XY stage having aparallel spring stage structure for XY scanning and an actuator 606which is attached to the XY stage for Z scanning. The XY stage havingthe parallel spring stage structure is disclosed in Jpn. Pat. Appln.KOKAI Publication No. 126110/1999, and its content is incorporated inthe present specification for reference.

The XY stage has a fixed table 601 and a movable table 607, and furtherincludes a pair of elastic members 608 and 609 provided on both sides ofthe movable table 607 along the Y axis, a pair of elastic members 610and 611 provided on both sides of the movable table 607 along the Xaxis, a pair of X direction actuators 602 and 603 for generatingdisplacement for moving the movable table 607 along the X axis, and apair of Y direction actuators 604 and 605 for generating displacementfor moving the movable table 607 along the Y axis.

Each of the elastic members 608 and 609 comprises, for example, arectangular spring which has a slit extending along the X axis and iselongated along the X axis. Further, each elastic member has relativelyhigh rigidity along the X axis and, on the other hand, relatively lowrigidity along the Y axis. Each of the elastic members 610 and 611comprises, for example, a rectangular spring which has a slit extendingalong the Y axis and is elongated along the Y axis. Each of theseelastic members has relatively high rigidity along the Y axis and, onthe other hand, relatively low rigidity along the X axis.

The elastic members 608 and 609, therefore, restrict movement of themovable table 607 along the X axis without largely limiting movement ofthe same along the Y axis. On the other hand, the elastic members 610and 611 restrict movement of the movable table 607 along the Y axiswithout largely limiting movement of the same along the X axis.

Additionally, the elastic members 608 and 609, the X direction actuators602 and 603, the elastic members 610 and 611, and the Y directionactuators 604 and 605 cooperate with each other to support the movabletable 607 so as to be maintained on the same plane. That is, theyrestrict movement of the movable table 607 along the Z axis. In otherwords, the elastic members 608 and 609, the X direction actuators 602and 603, the elastic members 610 and 611, and the Y direction actuators604 and 605 constitute a guide mechanism for restricting movement of themovable table 607 along the Z axis.

The actuator 606 in charge of Z scanning to which high speed scanning isrequired comprises, for example, a stacked piezoelectric device, andthis stacked piezoelectric device has a part in the vicinity of thecenter thereof being fixed to the movable table 607 by, e.g., anadhesive. Both side portions of the Z scanning stacked piezoelectricdevice 606 symmetrically extend and contract in the opposed directionsin response to application of a voltage, as indicated by the arrows,with its part close to the center thereof fixed to the movable table 607as a reference. The impact generated by the extending and contractingoperation of the stacked piezoelectric device 606 can be, therefore,suppressed. Accordingly, the scanning unit of this embodiment can stablyoperate with respect to high speed scanning with less vibrations.

A description will now be given as to comparative examples facilitatingunderstanding of advantages of the scanning unit according to thepresent invention hereinafter.

FIRST COMPARATIVE EXAMPLE

A first comparative example will be explained with reference to FIGS. 7Aand 7B. As shown in FIGS. 7A and 7B, the scanning unit of thiscomparative example comprises a scanning unit holding base 701, anL-shaped actuator pedestal 702 fixed to the scanning unit holding base701, two actuators 703 and 704 attached to the actuator pedestal 702,and an actuator 705 held by the two actuators 703 and 704.

Each of the actuators 703, 704 and 705 comprises, for example, a stackedpiezoelectric device and extendable along the X axis, the Y axis and theZ axis. Each of the X scanning stacked piezoelectric device 703 and theY scanning stacked piezoelectric device 704 has one end portion fixed tothe actuator pedestal 702. One end of the Z scanning stackedpiezoelectric device 705 is fixed to the other end of each of the Xscanning stacked piezoelectric device 703 and the Y scanning stackedpiezoelectric device 704 by an adhesive in order to obtain a longstroke, namely, a scanning range.

In this scanning unit, the extending and contracting operation of the Zscanning stacked piezoelectric device 705 generates the moment in the Xscanning and Y scanning stacked piezoelectric devices 703 and 704. Thisproduces the vibrations, and the generated vibrations are transmitted tothe actuator pedestal 702 or the scanning unit holding base 701 tooscillate the scanning unit.

The scanning unit of each of the foregoing embodiments has reducedvibration noise as compared with the scanning unit of this comparativeexample.

SECOND COMPARATIVE EXAMPLE

A second comparative example will now be described with reference toFIGS. 8A and 8B. As shown in FIGS. 8A and 8B, the scanning unit of thiscomparative example comprises a scanning unit holding base 801, anL-shaped actuator pedestal 802 fixed to the scanning unit holding base801, an X scanning actuator 803 fixed to the actuator pedestal 802, a Yscanning actuator 804 fixed to a free end portion of the X scanningactuator 803, and a Z scanning actuator 805 fixed to a free end portionof the Y scanning actuator 804.

Each of the actuators 803, 804 and 805 comprises, for example, a stackedpiezoelectric device, and these actuators are connected to each other inseries with their directions changed at 90 degrees in order to obtain along stroke, i.e., a scanning range.

In this scanning unit, the extending and contracting operation of the Zscanning stacked piezoelectric device 805 generates the moment to the Xscanning stacked piezoelectric device 804 or the X scanning stackedpiezoelectric device 803, as similar to the first comparative example.This produces the vibrations, and the generated vibrations aretransmitted to the actuator pedestal 802 or the scanning unit holdingbase 801, thereby oscillating the scanning unit.

The scanning unit of each of the foregoing embodiments has reducedvibration noise as compared with the scanning unit of this comparativeexample.

THIRD COMPARATIVE EXAMPLE

A third comparative example will now be described with reference toFIGS. 9A and 9B. As shown in FIGS. 9A and 9B, the scanning unit of thiscomparative example comprises a scanning unit holding base 901, anL-shaped actuator pedestal 902 fixed to the scanning unit holding base901, an X scanning actuator 903, a Y scanning actuator 904, and a Zscanning actuator 905. Each of the actuators 903, 904 and 905 comprises,for example, a stacked piezoelectric device and extendable along the Xaxis, the Y axis and the Z axis.

One end portion of each of the X scanning actuator 903 and the Yscanning actuator 904 is fixed to the actuator pedestal 902, and one endportion of the Z scanning actuator 905 is fixed to the scanning unitholding base 901. The other end portions of the three stackedpiezoelectric devices 903, 904 and 905 are connected to each other. Thatis, the scanning unit of this comparative example is of a so-calledtripod type which is the most common structure as the scanning unit ofthe scanning tunnel microscope.

In this scanning unit, the counteraction of the extending andcontracting operation of the Z scanning piezoelectric device 905 isdirectly transmitted to the scanning unit holding base 901 to oscillatethe scanning unit or twist the X scanning and Y scanning stackedpiezoelectric devices 903 and 904 out of shape. Further, the vibrationof that operation is transmitted to the actuator pedestal 902 tooscillate the scanning unit.

The scanning unit of each of the foregoing embodiments has reducedvibration noise as compared with the scanning unit of this comparativeexample.

Sixth Embodiment

A sixth embodiment according to the present invention will now bedescribed with reference to FIGS. 10A to 10C. FIG. 10A is a perspectiveview of a scanning unit of this embodiment; FIG. 10B, a view showingFIG. 10A from the direction of arrow A; and FIG. 10C, a view showingFIG. 10A from the direction of arrow B.

The scanning unit of this embodiment comprises a scanning unit holdingbase 1001 as a base plate, a first actuator holding portion 1006 fixedto the scanning unit holding base 1001, a Y scanning actuator 1002 whichis attached to the actuator holding portion 1006 and extendable alongthe Y axis, a block 1008 attached to the other end of the Y scanningactuator 1002, a second actuator holding portion 1009 fixed to the block1008, an X scanning actuator 1003 which is attached to the actuatorholding portion and extendable along the X axis, an actuator connectionportion 1011 attached to the other end of the X scanning actuator 1003,and two actuators 1004 and 1005 which are fixed to the actuatorconnection portion 1011 and extendable along the Z axis.

The two actuators 1004 and 1005 and the actuator connection portion 1011constitute the Z scanning actuator. To a free end side 1013 of theactuator 1004 constituting the Z scanning actuator is attached a sampleholding portion (similar to the sample holding portion 211 shown inFIGS. 2A to 2D) according to needs. The first actuator holding portion1006 is fixed to the scanning unit holding base 1001 by a screw 1007,and the second actuator holding portion 1009 is fixed to a block 1008 bya screw 1010.

Each of the actuators 1002, 1003, 1004 and 1005 comprises, for example,a stacked piezoelectric device, and has a length of 5 mm and a crosssection of 2 mm×3 mm. These actuators extend and contract uponapplication of a voltage of 100 V. Cylindrical piezoelectric devices maybe used for these actuators instead of the stacked piezoelectricdevices.

As can be understood from FIG. 10B or 10C, the block 1008 is distancedfrom the scanning unit holding base 1001 and can move along the Y axisin response to drive of the Y scanning actuator 1002. Further, as can beunderstood from FIG. 10B, the actuator connection portion 1011 does notcome into contact with the block 1008 and can move along the X axis inresponse to drive of the X scanning actuator 1003.

In order to suppress transmission of the vibration generated from highspeed scanning along the Z axis at a scanning frequency, namely, Zscanning to the X scanning actuator 1003 and the like, the two actuators1004 and 1005 constituting the Z scanning actuator are driven insynchronization with each other in the opposed directions with theactuator connection portion 1011 at the center.

The actuator 1005 under the Z scanning actuator extends in a throughhole (clearance hole) 1012 formed to the block 1008 without beingbrought into contact with the block 1008.

In a similar fashion to that of the second embodiment described withreference to FIG. 3B, since the two actuators 1004 and 1005 constitutingthe Z scanning actuator in the scanning unit of this embodimentsymmetrically extend and contract in opposed directions along the Zaxis, the impact generated by high speed Z scanning is balanced.Therefore, less vibrations are generated in the actuator connectionportion 1011 connecting the two actuators 1004 and 1005. Thus, the Xscanning actuator 1003 holding the actuator connection portion 1011 orthe Y scanning actuator 1002 holding the X scanning actuator 1003 aresubjected to less vibrations. As a result, this scanning unit can stablyoperate with respect to high speed scanning.

Moreover, the scanning unit 1000 of this embodiment comprises astructure obtained by folding the X scanning actuator from the left endof the block 1008 to the right side. The center of gravity of a partmounted on the block 1008 (including the X scanning actuator 1003, forexample) is positioned in the vicinity of the center axis of the Yscanning actuator (a line parallel to the extending and contractingdirection and running through the center of the cross section of theactuator). Thus, yawing hardly occurs with respect to Y scanning. Thispoint also contributes to an improvement of the stability at the time ofhigh speed scanning.

Seventh Embodiment

A seventh embodiment according to the present invention will now bedescribed with reference to FIG. 11. The basic structure of the scanningunit of this embodiment is similar to the scanning unit 1000 of thesixth embodiment described with reference to FIGS. 10A to 10C.

The scanning unit 1100 of this embodiment comprises a scanning unitholding base 1101 as a base plate, a first actuator holding portion 1106fixed to the scanning unit holding base 1101, a Y scanning actuator 1102which is attached to the actuator holding portion 1106 and extendablealong the Y axis, a block 1108 attached to the other end of the Yscanning actuator 1102, a second actuator holding portion 1109 fixed tothe block 1108, an X scanning actuator 1103 which is attached to theactuator holding portion 1109 and extendable along the X axis, anactuator connection portion 1111 attached to the other end of the Xscanning actuator 1103, and two actuators 1104 and 1105 which are fixedto the actuator connection portion 1111 and extendable along the Z axis.

The two actuators 1104 and 1105 and the actuator connection portion 1111constitute the Z scanning actuator. A sample holding portion (similar tothe sample holding portion 211 shown in FIGS. 2A to 2D) is attached to afree end side 1121 of the actuator 1104 constituting the Z scanningactuator according to needs. The actuator holding portion 1006 is fixedto the scanning unit holding base 1001 by a screw 1007.

The block 1108 is supported by elastic hinge mechanisms 1117 and 1118and block holding portions 1113 and 1114. The block holding portions1113 and 1114 are fixed to the scanning unit holding base 1101 by screws1115 and 1116. Each of the elastic hinge mechanisms 1117 and 1118 is amechanism having a spring property formed by alternately arranging athrough hole 1120 and a notched groove 1119 connected to this hole, andrestricts movement of the block 1108 along the X axis and the Z axiswithout largely limiting movement of the same along the Y axis. In otherwords, the elastic hinge mechanisms 1117 and 1118 constitute a guidemechanism restricting movement of the block 1108 along the Z axis, andthis guide mechanism suppresses generation of deflection of the Yscanning actuator 1102 along the Z axis.

In the scanning unit 1000 of the sixth embodiment illustrated in FIGS.10A to 10C, the sample holding portion is attached to an end portion1013 of the Z scanning actuator 1004 according to needs, and a sample isdetachably fixed to the sample holding portion. When replacing thesample, force pressing the sample in the −Z direction to fix the sampleis applied to the sample holding portion. Since the X scanning actuator1003 and the Y scanning actuator 1002 are substantially cantilevered,they may be possibly bent when the stress caused due to the moment ofthe force applied to the sample holding portion acts when replacing thesample. In particular, the joint portion of the Y scanning actuator 1002and the actuator holding portion 1006 can be easily bent. Therefore,sample replacement must be carefully carried out.

On the contrary, in the scanning unit 1100 of this embodiment shown inFIG. 11, the Y scanning actuator 1102 is supported in the centerimpeller manner by the block 1108 and the actuator holding portion 1107.As a result, the joint portion of the Y scanning actuator 1102 and theactuator holding portion 1106 which is apt to be bent in the scanningunit 1000 of the sixth embodiment is hardly bent. The center impellersupport prevents the Y scanning actuator 1102 from being deflected inthe gravitational force direction (−Z direction) by the weight of theunit provided thereon and avoids collapse of the orthogonality of theXYZ scanning by deflection.

In light of these viewpoints, it can be considered that the Y scanningunit of this embodiment has a guide mechanism using an elastic hingemechanism. Alternatively, considering the extension of a folded hingemechanism, it can be also considered that the Y scanning unit has aguide mechanism using a leaf spring mechanism. Further, it can be saidthat the guide mechanism constitutes a mechanism for reducing deflectionand vibrations of the actuator.

In a similar to that of the foregoing embodiments, since the twoactuators 1104 and 1105 constituting the Z scanning actuator in thescanning unit of this embodiment symmetrically extend and contract alongthe Z axis, the impact generated by high speed Z scanning can bebalanced. Thus, the scanning unit can stably operate with respect tohigh speed scanning with less vibrations generated from the scanningoperation.

In this embodiment, although the guide mechanism, i.e., the elastichinge is provided to the movable end side of the Y scanning actuator1102, the guide mechanism may be provided to the movable end side of theX scanning actuator 1103 so that deflection of the X scanning actuator1103 in the gravitational force direction can be prevented and thevibrations can be reduced.

Eighth Embodiment

An eighth embodiment according to the present invention will now bedescribed with reference to FIGS. 12A and 12B. FIG. 12A is a perspectiveview showing a scanning unit of this embodiment, and FIG. 12B is a sideview of FIG. 12A shown from the direction of arrow C.

The scanning unit 1200 of this embodiment comprises a scanning unitholding base 1201 as a base plate, a first actuator holding portion 1206fixed to the scanning unit holding base 1201, a Y scanning actuator 1202which is attached to the actuator holding portion 1206 and extendablealong the Y axis, a block 1208 attached to the other end of the Yscanning actuator 1202, a second actuator holding portion 1209 fixed tothe block 1208, an X scanning actuator 1203 which is attached to theactuator holding portion 1209 and extendable along the X axis, anactuator connection portion 1211 attached to the other end of the Xscanning actuator 1203, and two actuators 1204 and 1205 which are fixedto the actuator connection portion 1211 and extendable along the Z axis.

The two actuators 1204 and 1205 and the actuator connection portion 1211constitute the Z scanning actuator. A sample holding portion (similar tothe sample holding portion 211 shown in FIGS. 2A to 2D) is attached to afree end side 1226 of the actuator 1204 constituting the Z scanningactuator according to needs. The first actuator holding portion 1206 isfixed to the scanning unit holding base 1201 by a screw 1207, and thesecond actuator holding portion 1209 is fixed to the block 1208 by ascrew 1210.

As shown in FIG. 12B, the block 1208 which is moved along the Y axis inaccordance with drive by the Y scanning actuator 1202 is positionedbetween the scanning unit holding base 1201 and a first pressing plate1212 and sandwiched by minute balls 1216, 1222, 1224, 1225 and 1215 (seeFIG. 12A). A gap between the scanning unit holding base 1201 and thepressing plate 1212 is adjusted by screws 1213 and 1214 so that they canbe fixed in parallel with each other. As a result, the block 1208 is notlargely restricted in connection with movement along the Y axis, but itsmovement along the Z axis is limited.

In other words, the scanning unit of this embodiment has a minute ballrolling or sliding guide which restricts movement of the block 1208along the Z axis, and this guide has a scanning unit holding base 1201positioned under the block 1208, minute balls 1224 and 1225 positionedbetween the block 1208 and the scanning unit holding base 1201, apressing plate 1212 positioned above the block 1208, minute balls 1215,1216 and 1222 positioned between the block 1208 and the pressing plate1212, and screws 1213 and 1214 which cause the pressing plate 1212 andthe block 1208 to sandwich and the minute balls 1215, 1216, 1222, 1224and 1225 therebetween and presses the pressing plate 1212 and the block1208 against the scanning unit holding base 1201.

An actuator connection portion 1211 which is moved along the X axis inaccordance with drive by the X scanning actuator 1203 is positionedbetween the block 1208 and a second pressing plate 1217 and supported bythe minute poles 1219 and 1220 from the upper portion and by the minuteball 1221 from the lower portion so that its movement along the Z axisis restricted. A gap between the block 1208 and the pressing plate 1217is adjusted by the screws 1218 and 1227 so that they can be fixed inparallel with each other. Consequently, the actuator connection portion1211 is not largely restricted in regard to movement along the X axis,but its movement along the Z axis is limited.

In other words, the scanning unit of this embodiment has a minute ballrolling or sliding guide which restricts movement of the actuatorconnection portion 1211 along the Z axis, and this guide has a block1208 positioned below the actuator connection portion 1211, a minuteball 1221 positioned between the actuator connection portion 1211 andthe block 1208, a pressing plate 1217 positioned above the actuatorconnection portion 1211, a minute ball 1219 positioned between theactuator connection portion 1211 and the pressing plate 1217, and screws1218 and 1227 for pressing the pressing plate 1217 and the actuatorconnection portion 1211 against the block 1208 with the minute balls1219 and 12121 between the pressing plate 1217 and the actuatorconnection portion 1211.

As described above, in the scanning unit 1200 of this embodiment,deflection and vibrations of the Y scanning actuator 1202 are suppressedby a minute ball rolling or sliding guide including the pressing plate1212, the screws 1213 and 1214, and the minute balls 1216, 1215, 1222,1224 and 1225, and deflection and vibrations of the X scanning actuator1203 are suppressed by the minute ball rolling or sliding guideincluding the pressing plate 1217, the screws 1218 and 1227 and theminute balls 1219 and 1220.

U.S. Pat. No. 5,912,461 discloses a probe scanning unit of a scanningprobe microscope having a minute ball rolling or sliding guide. In thisscanning unit, a minute ball is arranged between a moving body which isa member to be scanned and an end surface of a movable end of eachactuator, and displacement of the actuator is indirectly transmitted tothe moving body through the minute ball. Furthermore, the moving bodyand each actuator are attracted to each other with the minute balltherebetween by a magnet or a spring.

On the contrary, in the scanning unit 1200 of this embodiment, a memberto be moved (for example, a block 1208) is directly connected to anactuator for driving this member (for example, a Y scanning actuator1202), and a minute ball rolling or sliding guide guides the member tobe moved in such a manner that scanning movement of this actuator is notrestricted.

Although each of the scanning unit of this embodiment and the scanningunit of U.S. Pat. No. 5,912,461 has the minute ball rolling or slidingguide, the both scanning units are structurally different from eachother in this regard. Since the scanning unit of this embodiment has ahigher mechanical rigidity and performs direct drive, the vibrations canbe reduced and scanning can be effected at a higher speed.

Moreover, the size of probe scanning unit of U.S. Pat. No. 5,912,461tends to be large since a mechanism for holding a moving body as amember to be scanned is included in a portion controlling scanning.Therefore, this scanning unit is not suitable for the high speedscanning application aimed at by the scanning unit according to thepresent invention. Additionally, in the structure using a magnet, thepossibility that the moving body may unintentionally come off can not bedenied, and the moving body must be carefully treated when used. Thus,this structure has a usability problem to a certain extent.

On the other hand, in the scanning unit of this embodiment, the block1208 as a member to be scanned and the actuator connection portion 1211have minute balls arranged on their side surfaces on both sides alongthe Z axis and are pressed from the outer side. That is, a mechanism forholding the member to be scanned is provided outside the portion incharge of scanning. It is, therefore, possible to minimize an increasein weight of the scanned portion, thus a possible reduction in scanningfrequency, due to increased weight, is avoided, making this scanningunit suitable for high speed scanning. In addition, the member to bescanned is free from the worry of it detaching, and the scanning unitcan be stably used.

Further, in the above-described embodiments, although the actuatorswhich are the piezoelectric devices have been exemplified, the technicalconcept of suppressing the generation of vibration by holding thekinetic system of the drive portion at a position in the vicinity of thecenter of gravity thereof can be also applied to other actuators. Forexample, this can be applied to an actuator which is of a voice coiltype, and similar advantages can be obtained by holding the kineticsystem at a position in the vicinity of the center of gravity thereof.

Furthermore, the scanning unit according to the present invention has anadvantage of enabling high speed operation while suppressing thevibration as well as an advantage of reducing the scanning noise,thereby decreasing undesirable drive sounds.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A scanning microscope for using a probe toobserve a surface of a sample, comprising: a probe arranged in thevicinity of a surface of a sample; a cantilever for supporting theprobe; a scanning unit for relatively scanning the probe and the sample;and a displacement detection system for detecting displacement of thecantilever based on the interaction of the probe and the sample, thescanning unit including: a first actuator for moving an object to bemoved which is either the probe or the sample along a first axis, thefirst actuator having a pair of end portions, the object being attachedto one of the end portions, the first actuator being held at a positionin the vicinity of the center in dimension or the center of gravitythereof; a second actuator for moving the object along a second axisdifferent from the first axis; and a third actuator for moving theobject along a third axis different from both the first axis and thesecond axis, the second actuator and the third actuator comprising acommon cylindrical piezoelectric actuator.
 2. A scanning microscope forusing a probe to observe a surface of a sample, comprising: a probearranged in the vicinity of a surface of a sample; a cantilever forsupporting the probe; a scanning unit for relatively scanning the probeand the sample; and a displacement detection system for detectingdisplacement of the cantilever based on the interaction of the probe andthe sample, the scanning unit including: a first actuator for moving anobject to be moved which is either the probe or the sample along a firstaxis, the first actuator having a pair of end portions, the object beingattached to one of the end portions, the first actuator being held at aposition in the vicinity of the center in dimension or the center ofgravity thereof; a movable member for holding the first actuator; asecond actuator for moving the movable member along a second axisdifferent from the first axis; a third actuator for moving the movablemember along a third axis different from both the first axis and thesecond axis; and a guide mechanism for restricting movement of themovable member along the first axis.
 3. A scanning microscope for usinga probe to observe a surface of a sample, comprising: a probe arrangedin the vicinity of a surface of a sample; a cantilever for supportingthe probe; a scanning unit for relatively scanning the probe and thesample; and a displacement detection system for detecting displacementof the cantilever based on the interaction of the probe and the sample,the scanning unit including: a first actuator for moving an object to bemoved which is either the probe or the sample along a first axis, thefirst actuator having a pair of end portions, the object being attachedto one of the end portions, the first actuator being held at a positionin the vicinity of the center in dimension or the center of gravitythereof; a second actuator for moving the object along a second axisdifferent from the first axis, the second actuator having a pair of endportions, one of the end portions being connected to the first actuator;a movable member for supporting the second actuator; a third actuatorfor moving the object along a third axis different from both the firstaxis and the second axis, the third actuator having a pair of endportions, one of the end portions being connected to a movable member tosupport the movable member, the other one of the end portions beingfixed; and a guide mechanism for restricting movement of the movablemember along the first axis.